Problem: William eats at a cafe and the cost of his meal is $\$24.00$. He would like to leave a $20\%$ tip. What is his total bill including tip?
Answer: The tip amount is equal to $20\% \times \$24.00$ We can find the tip by first calculating a $10\%$ tip and then multiplying that number by two. To calculate a $10\%$ tip, move the decimal point in $\$24.00$ one place to the left. $10\%$ $\times \$24.00$ $\$2.40$ To calculate a $20\%$ tip, multiply the $10\%$ tip amount by two. $20\%$ $\times \$24.00$ $\$2.40$ $ \times 2 = $ $\$4.80$ The cost of the meal plus the amount of the tip will equal the total bill amount. $\$24.00 + \$4.80 = $ $\$28.80$ The total cost of the bill is $\$28.80$.